you can open the ports at "Virtual servers"

You can't do it with the factory firmware... but you can do it with ddwrt. DDwrt supports the archer c9. Here is a page how to setup the phone as a second wan port on ddwrt :...

Hi Dale 1. Yes ! 2. Multihomed devices (you mean the two nic devices?) will be fine, because of the local routing table on your home server and your synology. You can choose on the multihomed devices...

these devices are outside ? did you install/connected the grounding ?